KABUL, Afghanistan: Afghanistan's president has warned that civilian casualties caused by NATO airstrikes could undermine the cooperation agreement he just signed with the U.S. He talked to families of the latest victims on Tuesday.

Also on Tuesday, Taliban attacks in three provinces killed 12 Afghans — seven police, four Education Ministry employees and a bodyguard.

The Taliban kill more civilians than foreign forces, but the deaths of citizens caught in the crossfire of the decade-long war continue to be an irritant in President Hamid Karzai's relationship with his international partners. Any NATO airstrike that leads to civilian deaths also erodes the Afghan people's trust in foreign forces.

"If the lives of Afghan people are not safe, the signing of the strategic partnership has no meaning," Karzai's office said in a statement released Monday evening.

The long-term strategic partnership, which Karzai and President Barack Obama signed earlier this month, governs the relationship between the two countries from the end of 2014 until 2024.

According to Afghan officials, 18 civilians have died in four airstrikes since Thursday in Logar, Kapisa, Badghis and Helmand provinces.

"The families of the recent victims asked Karzai to tell the foreign troops to stop the bombardment of houses and the killing of civilians," the statement said.

Last year was the deadliest on record for civilians in the Afghan war, with 3,021 killed as insurgents ratcheted up violence with suicide attacks and roadside bombs, the United Nations said in its latest report on civilian deaths.

The U.N. attributed 77 percent of the deaths to insurgent attacks and 14 percent to actions by international and Afghan troops. Nine percent of cases were classified as having an unknown cause.

While the total number of civilian deaths caused by international and Afghan forces dropped, the number of civilians killed by airstrikes targeting insurgents rose to 187 in 2011, accounting for nearly half the deaths attributed to forces supporting the government.

Lt. Col. Jimmie Cummings, a spokesman for the U.S.-led NATO coalition, said the recent airstrikes were under investigation and that if NATO forces were to blame, U.S. Marine Gen. John Allen, the top commander of American and NATO forces in Afghanistan, would "take personal responsibility" for the incidents.

"We have committed to fully investigating the exact circumstances surrounding these events and reporting back to President Karzai," Cummings said. "The coalition will continue to take any and all appropriate actions to minimize the likelihood of this happening again. This coalition is here to build a safe and secure environment for the Afghan people. ... and we take any allegations of civilian causalities very seriously."

In other violence, four Education Ministry employees and a bodyguard were shot and killed by Taliban militants in eastern Paktika province. Khorshid Aman, the chief of Urgun district, said the group was traveling from the district to the provincial capital of Sharan when the militants ambushed their two vehicles.

Five police officers were killed when their vehicle hit a roadside mine in Pusht Rod district of Farah province in western Afghanistan, said Ghulam Gawas Malayar, deputy provincial police chief.

Din Mohammad Darwesh, a spokesman for the governor of Logar province in the east, said two other police officers were killed when Taliban militants ambushed them in a bazaar near the provincial capital of Pul-e-Alam.